Variable voltage transformer system



Feb- II, 1947- 2. 0.5T. PALLEY 2,415,712

VARIABLE VOLTAGE TRANSFORMER SYSTEM Filed May 25, 1944 3Sheecs-Sheet 1 Fig. 2.

MNMCMHS 7" III TRANSFOHMEH Inventor: Zoltan O. St. Pal leg,

H is Attorney.

Feb. 11, 1-947. 2. 0. s1. PALLEY 2,415,712

VARIABLE VOLTAGE TRANSFORMER SYSTEM Filed May 25, 1944 s sheets-sheet 2 F ig. 3.

MAIN WIND/N6 Fig. 4.

34/765 7085 6208.60 glam/-50 B) TERTIARY WIND/N6 60V AUTO THAMSFOHHEH Inventor: Zoltan 0. St. Pal leg,

Feb. 11, 1947.

Z. 0. ST. PALLEY VARIABLE VOLTAGE TRANSFORMER SYSTEM 1 BALANCING THANSFMHER 240v Filed May 25, 1944 3 Sheets-Sheet 3 fig. 6;

VOLTAGE mm; OBTAl/VED BY Rial/4709 CON 7A C7088 CL 0850 nEvgRs/Ale AND SHORT C [RC l/l TING SWITCH Inventor: Z0 ltan O.

His Attorne Patented Feb. 11, 1947 VARIABLE VOLTAGE TRANSFQRMEB SYSTEM Zoltan 0. St. Palley, Pittsfield, Mass, assignor to General Electric Company, a corporation oi New York Application May 25, 1944, Serial No. 537,258

8 Claims.

This invention relates to variable voltage trans former systems and more particularly to improvements in load-ratio-control systems.

Load-ratio-control means the control of the ratio of a transformer under load, and this invention relates to an improved wide voltage range system of this type having a large number of relatively small voltage steps. The invention is particularly well adapted, to the control of the motor voltage in electric locomotives.

The invention is characterized by a main transformer winding having a relatively few taps for providing large steps of voltage control in combination with a floating winding having a relatively small number of taps for pro ducing relatively coarse Vernier voltage control in further combination with a balancing transformer whose voltage is varied in still smaller steps to provide relatively fine Vernier voltage control. in addition, the voltage control of the balancing transformer is used to minimize the voltage interrupting duty of the tap contactors for the fi"=8.ting winding and the tap contactors of the floating Winding in combination with the voltage control of the balancing transformer are use-cl to minimize the voltage interrupting duty of the contactors for the taps of the main wind- An object of the invention is to provide a new and improved variable voltage transformer system.

Another object of the invention is to provide an improved wide-voltage-range small-voltagestep lcad-ratio-control system.

A further object of the invention is to provide a load-ratic-control system having a multiple Vernier voltage control.

The invention will be better understood from the following description taken in connection with the accompanying drawings and its scope will be pointed out in the appended claims.

In the drawings, Fig. 1. illustrates diagrammatically an embodiment of the invention, Fig. 2 is a table for indicating the various sequential operating positions of the parts of Fig. 1, Fig. is a modification in which a rotary commutator is used for controlling the voltage of the balanctransrormer, Fig. i is a table for indicating the various operating positions of the parts of Fig, 3, Fig. 5 is another modification which utilizes an induction regulator for controlling the voltage of the balancing transformer and which also uses a tickler winding, and Fig. 6 is a table for indicating the various operating positions of the parts of Fig. 5.

2 Referring now to the drawings and more particularly to Fig. 1, the transformer system is shown as consisting of a main winding which will ordinarily, although not necessarily, be the low voltage secondary winding of a voltage step down power transformer. Associated with this main winding and preferably on the same core is a floating winding having three electrically equally spaced taps connected respectively to contactors l, 2 and 3, the main winding being provided with electrically equally spaced taps which are connected respectively to contactors 4, 5, 55, l, 8, e and it. The voltage of the floating winding is less than the voltage between adjacent taps of the main winding and in fact it is less than the voltage between adjacent taps of the main winding by the voltage difierence between adjacent taps in the floating winding. Thus, if for purposes of illustration it is assumed that the voltage between electrically adjacent taps of the floating winding is 10 volts, then the total voltage of the floating winding is volts and the voltage between adjacent taps of the main winding is 120 volts plus 40 volts or volts. Ihe co-ntactors l, 3, $3 and Ill are connected to one terminal of the floating winding by a conductor 5! and the contactors 4, 5 and 6 are connected to the contactor 2 for the floating winding by a conductor 12.

Fine voltage control is obtained by a balancing transformer, one point of which is connected to the contactors l and 3 for the floating winding by a conductor i3 and another point of which is connected to the contactor 2 of the floating winding by a conductor M. An external circuit for the system has one conductor i5 connected to a terminal of the main winding and has another conductor it connected to the electrical mid-point of the balancing transformer. The maximum voltage of the balancing transformer between conductors l3 and I4 is equal to the voltage difference between adjacent taps of the floating winding, namely, 40 volts in the case of the illustrative voltage values which have already been assumed. The balancing transformer is excited by a tertiary winding on the main transformer and its voltage is varied by means of three two-position arcing duty contactors A, B and C, the two positions of these contactors being designated respectively as a and b. The balancing transformer is shown as a voltage step-down autotransformer, one terminal of whose primary winding is connected to the mid-point of the tertiary winding. The other terminal of the primary winding of the balancing transformer is connected to the mid-point of a reactor whose terminals are connected to the movable or common contact of the contactors A and B. Thus, the contactors A and B selectively connect the right-hand terminal of the primary winding of the balancing transformer to either the mid-point of the tertiary winding or to one of its terminals, depending upon the position of the contactor C which has a contact terminal ll connected respectively to corresponding fixed contacts of the contactors A and B. The voltage step-down ratio of the bal ancing transformer is shown for example as 22l so that it has an 80-volt primary winding, and consequently the tertiary winding has a 160 volt rating as only one-half of it at a time is connected across the primary winding of the balancing transformer. Similarly, the reactor has an 80-volt rating as it is never connected across more than one-half of the tertiary winding.

The main winding is shown as having an untapped end section between the conductor I and its tapped portion and for purposes of explanation it will be assumed that this is a 120-volt section.

The operation of Fig. 1 can best be understood by reference to the table shown in Fig. 2. Considering first position I, this calls for the contactors A, B and C being in their at positions and calls for contactors l and 7 being closed. Under these conditions the voltage between conductors l5 and I6 is 140 volts, this being made up of the voltage of the 120-volt end section of the main winding plus the first lO-volt section of the floating winding minus 20 volts in the balancing transformer between conductors l 3 and Hi. This negative 20 volts exists because the two terminals of the reactor are connected through contactors A, B and C tothe top terminal of the tertiary winding and as the mid-point of the tertiary winding is connected to the left-hand terminal of the primary of the balancing transformer the balancing transformer has maximum excitation in such direction that the voltage of the section of its secondary winding between conductors l3 and i6 bucks the voltage of the main and floating windings. In position 2 of the table shown in Fig, 2 contactor A is moved to its 1) position. This connects the terminals of the reactor across the upper half of the tertiary winding so that the reactor acts like an autotransformer and reduces the voltage difference between the terminals of the primary winding of the balancing transformer to half its former value or 40 volts. Consequently, the voltage of the section of the secondary winding of the balancing transformer between conductors l3 and i6 is now only volts in the bucking direction so that the voltage between the circuit conductors l5 and i6 is made up of 120 volts plus 40 volts minus 10 volts, thus making 150 volts, as shown in the table. In position 3 of the table contactor B has been moved to its 17 position, thus short circuiting the reactor and alsoshort circuiting the balancing transformer through the short-circuited reactor because both terminals of the reactor are now connected to the mid-point of the tertiary winding. Consequently, the voltage of the balancing transformer is zero and the voltage between main circuit conductors l5 and leis increased another 10 volts it now being merely the sum of the 120-volt section of the main winding and the 40-volt section of the floatin winding. In position 4 of the table contactor B has been moved back to its a position and contactor C has been moved to its 22 position,

thus connecting the reactor across the lower half of the tertiary winding and therefore reversing the balancing transformer voltage but applying: only 40 volts to its primary winding so that thereis only a 10-volt boost between conductors l 3 and i6, and this therefore raises the output voltage to volts. In position 5 contactor A is moved from its b to its a position, thus connecting both terminals of the reactor to the lower terminal of the tertiary winding which causes the balancing transformer to produce a 20-volt boost and thus raise the output circuit voltage to volts. In this position the voltage across the contacts of contactor 2 is zero because the voltage of'the secondary winding of the balancing transformer is 40 volts and it is of the same polarity as the voltage of the floating winding so that it is equal and opposite to the voltage between the taps for contactors l and 2. Consequently, contactor 2 is closed in position 5 and immediately thereafter contactor I is opened. Moreover, the opening of contactor 1 produces no change in circuit voltage because the voltage of the balancing winding between conductors I4 and I6 is 20 volts in the bucking direction so that the circuit voltage is made up of 120 volts plus 40 volts plus 40 volts minus 20 volts equals 180 volts as before.

The above cycle of operation of the contactors A, B and C is repeated twice through steps B-IZ, inclusive, the contactor 3 being closed and then the contactor 2 being opened in position 9. It will be noted that at this time the balancing transformer voltage also equals the voltage between the taps for contactors 2 and 3 so that contactor 3 closes and contactor .2 opens without having to interrupt any net transformer voltage.

In position l3 contactor 4 is connected to contactor I through all of the floating winding and through the balancing transformer with its voltage maximum and of the same polarity as the floating winding so the sum of the voltages of the floating winding and the balancing transformer equals the voltage between the taps for contactors 1 and 4, and consequently in position l3 contactor 4 is closed and contactor l is opened immediately thereafter. Also, in this position contactor 3 for the floating winding is opened. In position M the arcing contactors A and B are moved to their b positions, thus reducing the balancing transformer voltage to zero. Consequently, ther is no voltage difference between the contacts of contactor 8 and accordingly this contactor is closed in position 14.

The above cycle of operation is repeated for the other contactors of the main winding, the floating winding and the balancin transformer in each case cooperating to reduce the resultant transformer voltage to zero across the contacts of each contactor before it is opened or closed.

Although beginning with position i 4 the voltage is shown as being changed in 20-volt steps and beginning with position 28 it is shown as bein changed in all-volt steps, it will be obvious to those skilled in the art that throughout the entire range the change can be made in 10-volt steps just as is done for positions l-l3, inclusive. These Ill-volt steps are of course obtained by the operation of the contactors A, B and C.

It is desirable that the reactor of Fig. 1 be so constructed that it will not saturate even at maximum values of current so as to avoid excessive current rushes and peak voltages.

The cyclic and sequential actuation of the contactors can be done in any suitable way as by id electro pneumatic means of well known construction.

In the modification shown in Fig. 3 the reactor and arcing contactors A, B and C of Fig. 1 have been replaced by an 80-volt autotransformer and a commutator-type tap changer having a plurality of contact bars i8 connected in a regular order to equally-spaced taps in the autotransformer winding. This autotransformer winding is connected directly to the tertiary winding so as to be excited therefrom. The commutator bars engaged by two brushes !9 and 2B which are displaced 180 degrees and which have separate slip rings whereby they are connected to the terminals of the primary winding of the balancing transformer. In this manner rotation of the brushes progressively raises and lowers the vol"- age of the balancing transformer and also reverses its polarity.

The operation of Fig. 3 is given in the table shown in Fig. a, intermediate voltages between the limiting voltages for each position being obtained by the rotation of the brushes relative to the commutator bars. For example, assume that the system is in position 6 of Fig. 4; that is, the balancing transformer is connected to the main transformer through the contactors 2 and 3. The voltage of the main transformer, corresponding to this position, is 360 volts. In the position of the brushes shown in Fig. 3, the balancing transormer introduces 20 volts into the circuit of conductors ll; and it. Hence the resultant cii cuit voltage will be 340 volts. By rotating the brushes clockwise 90 degrees the excitation of the balancing transformer is decreased gradually to zero, thus raising the main circuit voltage gradually to 360 volts. The continued clockwise rotation causes further increase of the main circuit voltage until at 180 degree brush rotation the main circuit voltage will be 380 volts. In this position of the brushes the voltage across the secondary winding of the balancing transformer is 40 volts. Hence, contactor 3 can be closed without voltage change and without cur rent rush. Following this contactor 2 can be opened without change in voltage, hence without arcing. This sequence, continued with a clockwise rotation of the brushes, will boost the voltage, while a counterclockwise rotation will result in a lowering of the voltage.

roper coordination of the commutator the contactors can be obtained by any suitable mechanical connection between the commutater brushes and a suitable controller for operating the contactors. As the complete range requires onl 7 revolutions of the brushes, fast operation essential in locomotive control can be obtained without difficulty.

In Fig. the fine Vernier voltage control is obtained by means of an induction regulator which is excited from an auxiliary transformer winding which is connected in series with the main and floating windings. This induction voltage regulator energizes the primary winding of the balancing transformer through a reversing switch which is provided with means for short circuiting the windings which it interconnects, in its intermediate position.

In addition, the system is provided with a tickler winding which is shown as a ED-volt winding which is connected across 40-volt taps in the auxiliary winding and which has a mid-tap so as to provide an effective ZO-volt tickler winding. This 20-volt tickler winding is connected in seties with the conductor [3 and the left-hand half of the secondary winding of the balancing transformer.

The operation of Fig. 5 is set forth in the table shown in Fig. 6. The intermediate voltages between the limiting values shown for each position are obtained by rotation of the induction regulator so that the voltage may be varied in infinitely small steps.

Assume, for example, that the system is in position t of 6 and the induction regulator gives zero voltage with the windings short circuited by the reversing switch. The corresponding main circuit voltage is 200 volts. If the regulator is rotated clockwise the reversing switch moves into the boost position and the regulator gradually increases the excitation of the balancing transformer until a 10-volt boost is produced. In this position contactor 22 can be closed and contactor 2| can be opened without change in voltage. Similarly, counterclockwise rotation of the regulator will lower the main circuit voltage. The complete voltage range requires 30 revolutions of the rotor of the induction regulator. The proper timing of the regulator and the tap contactors may be obtained by any suitable mechanical interconnections of the rotor of the regulator and a controller for the contactors.

While there have been shown and described particular embodiments of this invention, it will be obvious to those skilled in the art that various changes and modifications can be made therein without departing from the invention and, therefore, it is aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent in the United States is:

1. In combination, a voltage step-down power transformer having a multi-tapped main low voltage winding, a balancing transformer, a niulti-tapped floating winding on power transformer, tap-changing contactors for selectively connecting the taps or said winding to said balancing transformer through floating winding to provide voltage steps, tapchanging contactors for cooperating with the taps of said floating winding for varying the effective turns of said floating winding to provide a series of relatively coarse Vernier voltage steps, means excited by said power transformer for varying the voltage of said balancing transformer to provide a series of relatively fine Vernier voltage steps, and a load circuit having conductors conn cted respectively to said main winding and to said balancing transformer.

2. In combination, a voltage step-down power transformer having a multi-tapped main low voltage winding, a balancing transformer, a multi-tapped floating winding on said power transformer, tap-changing contactors for selectively connecting the taps of said main winding to said balancing traasforiner through said floating win-ding to provide coarse voltage steps, tapchanging contactors for cooperating with the taps of said floating winding for varying the effective turns of said floating winding to provide a series of relatively coarse Vernier voltage steps, means excited by power transformer for varying the voltage of said balancing transformer to provide a series of relatively fine Vernier voltage steps, and a, load circuit having conductors connected respectively to said main winding and to said balancing transformer, the maximum balancing transformer voltage equalling one of said relatively coarse Vernier voltage steps whereby the tap-changing contactors for the floating winding operate with minimum voltage across their contacts, the floating winding voltage plus the maximum balancing transformer Voltage equalling the relatively coarse voltage steps whereby the tap-changing contactors for the main winding operate with minimum voltage across their contacts.

3. In combination, a main transformer Winding having a plurality of electrically equally spaced taps, a second transformer winding having a plurality of taps for dividing it into 11 equal voltage sections such that (11+ 1) times the voltage of one section equals the voltage between electrically adjacent taps of said main windin a third transformer winding, means for varying the voltage of said third winding in steps between a value equal to the voltage of one of said sections with one polarity and the same voltage with the opposite polarity, an external circuit connected between a point on said main winding and the electrical midpoint of said third winding, contactors connected to said taps, and interconnections between said contactors and said third transformer winding, said contactors for the taps of said main transformer winding being operated only when the sum of the effective voltages of said second and third windings equals the voltage dilference between successively operated ones of said contactors for the taps of said main winding, the contactors for the taps of said second winding being operated only when the voltage of said third winding is equal and opposite to the voltage difference between successively operated ones of the contactors for the taps of said second winding.

l. In combination, an alternating current circuit having twoconductors, a transformer winding having a point thereon connected to one of said conductors, said Winding having a plurality of electrically equally-spaced taps, a second transformer winding having an intermediate point thereon connected to the other of said circuit conductors, circuit making and breaking means for selectively connecting said taps to a second point in said second transformer winding, a third transformer winding having a plurality of electrically equally-spaced taps, additional circuit making and breaking means for selectively con-- necting said tape to a point in said third winding, and additional circuit making and breaking means for selectively connecting the even-numbered taps of said third transformer winding to said second point in said second transformer winding and alternately selectively connecting the odd-numbered taps of said third transformer winding to a third point in said second transformer winding, said intermediate point in said second winding being electrically equally spaced from said second and third points.

5. In combination, a transformer winding, a reactor winding, a circuit connected respectively to the electrical midpoints of said windings, a twoposition contactor for selectively connecting a contact terminal with the terminals of said transformer winding, a second two-position contactor for selectively connecting a terminal of said reactor winding to the midpoint of said transformer winding and to said contact terminal, and a third contactor for selectively connecting the remaining terminal of said reactor winding to the midpoint of said transformer winding and to said contact terminal.

6. In combination, a voltage step-down power transformer having a multi-tapped main low voltage winding, a balancing transformer, a multi-tapped floating winding on said transformer, tap-changing contactors for selectively connecting the taps of said main winding to said balancing transformer through said floating winding to provide coarse voltage steps, tap-changing contactors for cooperating with the taps of said floating winding for varying the effective turns of said floating winding to provide a series of relatively coarse Vernier voltage steps, a tertiary winding on said transformer provided with areing duty tap-changing means for varying the voltage of said balancing transformer to provide a series of relatively fine Vernier voltage steps, and a load circuit having conductors connected respectively to said main winding and to said balancing transformer.

7. In combination, a voltage step-down power transformer having a multi-tapped main low voltage winding, a balancing transformer, a multi-tapped floating winding on said transformer, tap-changing contactors for selectively connecting the taps of said main winding to said balancing transformer through said floating winding to provide coarse voltage steps, tapchanging contactors for cooperating with the taps of said floating winding for varying the effective turns of said floating winding to provide a series of relatively coarse Vernier voltage steps, means including a rotary commutator type tap changer for varying the voltage of said balancing transformer to provide a series of relatively fine Vernier voltage steps, and a load circuit having conductors connected respectively to said main winding and to said balancing transformer.

8. In combination, a voltage step-down power transformer having a multi-tapped main low voltage Winding, a balancing transformer, a mu1titapped floating winding on said transformer, tapchanging contactors for selectively connecting the taps of said main winding to said balancing transformer through said floating winding to provide coarse voltage steps, tap-changin contactors for cooperating with the taps of said floating winding for varying the eflective turns of said floating winding to provide a series of relatively coarse Vernier voltage steps, means including an induction voltage regulator for varying thevoltage of said balancing transformer to provide a series of relatively fine Vernier voltage steps, and a load circuit having conductors connected respectively to said main winding and to said balancing transformer.

ZOLTAN 0. ST. PALLEY.

REFERENCES CITED The following references are of record in the flle of this patent:

UNITED STATES PATENTS Number I Name Date 2,361,201 Hibbard Oct. 24, 1944 1,905,249 Snyder Apr. 25, 1933 

